Thermal properties of extruded/injection-molded poly(lactic acid) and biobased composites

Poly(Lactic Acid)-Poly(Butylene Succinate)-Sugar Beet Pulp Composites; Part I: Mechanics of Composites with Fine and Coarse Sugar Beet Pulp Particles

Sugar beet pulp (SBP) is a residue available in large quantities from the sugar industry, and can serve as a cost-effective bio-based and biodegradable filler for fully bio-based compounds based on bio-based polyesters. The heterogeneous cell structure of sugar beet suggests that the processing of SBP can affect the properties of the composite. An "Ultra-Rotor" type air turbulence mill was used to produce SBP particles of different sizes. These particles were processed in a twin-screw extruder with poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) and fillers to granules for possible marketable formulations. Different screw designs, compatibilizers and the use of glycerol as a thermoplasticization agent for SBP were also tested. The spherical, cubic, or ellipsoidal-like shaped particles of SBP are not suitable for usage as a fiber-like reinforcement. In addition, the fineness of ground SBP affects the mechanical properties because (i) a high proportion of polar surfaces leads to poor compatibility, and (ii) due to the inner structure of the particulate matter, the strength of the composite is limited to the cohesive strength of compressed sugar-cell compartments of the SBP. The compatibilization of the polymer-matrix-particle interface can be achieved by using compatibilizers of different types. Scanning electron microscopy (SEM) fracture patterns show that the compatibilization can lead to both well-bonded particles and cohesive fracture patterns in the matrix. Nevertheless, the mechanical properties are limited by the impact and elongation behavior. Therefore, the applications of SBP-based composites must be well considered.

Development of recycled polylactic acid/oyster shell/biomass waste composite for green packaging materials with pure natural glue and nano-fluid

In this study, a diversified waste recycling system and a green processing technology are proposed. This research not only finds feasible solutions to alleviate environmental problems of plastic pollution and straw burning but also provides new reuse methods for oyster shell waste and hogwash oil. The developed noval biocomposite material is conducive to the green development of express industry. This paper evaluates the performance of materials from many aspects: X-ray computed tomography characterization, fundamental physical properties, mechanical properties, microscopic morphology, SEM morphology, and comprehensive performance of products. Two kinds of products with economic value are found. One is sample 4, which is suitable for making granular products due to its low cost (0.328$/500 g). Another is sample 13, which is suitable for manufacturing green packaging materials due to its excellent mechanical properties (tensile strength 14.15 MPa; elongation at break 12.68%; Young's modulus 8189.89 MPa). Based on the experimental results, the process of the composite is simulated to study the different strengthening mechanisms of arabic gum and poly(methyl vinyl ether-alt-maleic anhydride). Arabic gum uses chemical reaction and principle of similarity and intermiscibility to fuse with biomass to form homogeneous hybrid in the form of liquid gel. Poly(methyl vinyl ether-alt-maleic anhydride) indirectly adheres filler to the matrix through ring-opening reaction and structural similarity. The new emulsification system caused by arabic gum promotes the arabic gum and nano-fluid coupling cross-linking system to produce a decentralized cross-linked network and inhibit the pernicious molecular chain entanglement.

Studies on durability of sustainable biobased composites: a review

This review provides a comprehensive discussion on the long-term durability performance and degradation behaviour of the increasingly popular sustainable biobased composites under various aging environments.

Polylactide-based renewable green composites from agricultural residues and their hybrids

Agricultural natural fibers like jute, kenaf, sisal, flax, and industrial hemp have been extensively studied in green composites. The continuous supply of biofibers in high volumes to automotive part makers has raised concerns. Because extrusion followed by injection molding drastically reduces the aspect ratio of biofibers, the mechanical performance of injection molded agricultural residue and agricultural fiber-based composites are comparable. Here, the use of inexpensive agricultural residues and their hybrids that are 8-10 times cheaper than agricultural fibers is demonstrated to be a better way of getting sustainable materials with better performance. Green renewable composites from polylactide (PLA), agricultural residues (wheat straw, corn stover, soy stalks, and their hybrids) were successfully prepared through twin-screw extrusion, followed by injection molding. The effect on mechanical properties of varying the wheat straw amount from 10 to 40 wt % in PLA-wheat straw composites was studied. Tensile moduli were compared with theoretical calculations from the rule of mixture (ROM). Combination of agricultural residues as hybrids is proved to reduce the supply chain concerns for injection molded green composites. Densities of the green composites were found to be lower than those of conventional glass fiber composites.

Thermo-mechanical processing of sugar beet pulp. III. Study of extruded films improvement with various plasticizers and cross-linkers

Thermoplastic sugar beet pulp (thermo-mechanical processing was discussed in previous studies) was formed into film strips by extrusion. Film tensile properties are discussed according to the molecular structure of external plasticizer. Sorbitol, fructose and adipic acid have a marked antiplasticizing effect, while urea and xylitol gave higher ultimate tensile stress than glycerol for a comparable strain at break. Xylitol can be considered as the best plasticizer with UTS and EL of, respectively, 4.9 MPa and 11.3% and water absorption (85% RH, 25 degrees C) was less than 25%. Glycidyl methacrylate was directly used in the extrusion process as cross-linker. In high humidity atmosphere (97% RH, 25 degrees C), film water absorption was then kept under 40% while tensile strength and strain were improved of 50% and with a 30 min UV post-treatment the mass gain in absorption was even less than 30% after 5 days.

Mechanical and thermal properties of green polylactide composites with natural fillers

Green composites of PLA with micropowders derived from agricultural by-products such as oat husks, cocoa shells, and apple solids that remain after pressing have been prepared by melt mixing. The thermal and mechanical properties of the composites, including the effect of matrix crystallization and plasticization with poly(propylene glycol), have been studied. All fillers nucleated PLA crystallization and decreased the cold-crystallization temperature. They also affected the mechanical properties of the compositions, increasing the modulus of elasticity but decreasing the elongation at break and tensile impact strength although with few exceptions. Plasticization of the PLA matrix improved the ductility of the composites.